This invention relates to novel addition products of isocyanates with oxyalkylene-substituted aminophenol compounds as intermediates for the production of urethane-substituted xanthene colorants, particularly triphenylmethane derivatives such as rhodamines. The xanthene colorants exhibit improved wax and/or oil solubility and high purity. The urethane-substituted xanthene colorant features very good wax and/or oil solubility, and is believed to be relatively nontoxic. A method for producing this novel colorant is also provided.
All U.S. patents cited within this specification are hereby incorporated by reference.
Xanthene dyes, and in particular rhodamine dyes, are well known in the art as exemplified in the COLOUR INDEX, 3rd. ed., Vol. 4, pp. 4419-4422 (1971). These dyes range from bright red to bright bluish red, and typically fluoresce orange or red upon exposure to ultraviolet light. Most importantly, such rhodamines provide magenta colorations for various coloring systems. Rhodamine dyes are useful in a variety of applications including coloring soaps and other cleaning products, water tracing and leak detection. While such dyes have been utilized within certain portions of the colorant industry, their use has been limited due to toxicity issues. Thus, they are generally unsuitable for use when human exposure to such a dye is likely. Less toxic rhodamines have been developed, such as Rhodamine WT, available from Abbey Color Products. However, such a low-toxicity rhodamine exhibits relatively poor light fastness, as well as poor solubility in non polar media.
Another category of available xanthene dyes for colorant uses, particularly triphenylmethane type-xanthenes, is exemplified by the fluoran compounds disclosed in Farber et al., U.S. Pat. No. 3,873,573; Hatano et al., U.S. Pat. No. 4,330,473; and Zink, U.S. Pat. No. 4,806,657. The compounds are diamino-xanthene dyes having amino groups in the 3- and 7-positions, including phenyl-substituted amino groups. These patents also disclose p-methoxy-N-phenylaniline intermediates which may be reacted with a ketonic acid. Such dyes are particularly useful as recording material, since the lactone ring within these xanthene compounds are susceptible to opening thereby converting the faintly colored material to a dark green or black color.
Typical prior art processes for manufacturing rhodamine dyes provide for condensing m-dialkylaminophenol with phthalic anhydride. In synthesizing a poly(oxyalkylene) substituted colorant, it is desirable to alkoxylate one or more of the reactants or intermediates which form the colorant. However, the intermediates used in a typical rhodamine synthesis may not be readily alkoxylated without adding poly(oxylakylene) to sites on the intermediate which participate in colorant formation. U.S. Pat. No. 5,250,708 teaches us of a process to produce a specific oxyalkylene substituted aminophenol intermediate that is successfully used in the production of poly(oxyalkylene)-substituted xanthene colorant. U.S. Pat. No. 5,919,846, U.S. Pat. No. 5,919,839, and PCT patent Application WO 94/14902 describes the reaction of hydroxyl containing colorants with mono and diisocyanates.
More versatile xanthene colorants have been produced for ink applications. Such xanthenes include those taught within U.S. Pat. No. 5,250,708 which teaches a method of producing a poly(oxyalkylene) xanthene colorant by reacting 2-(4-N,N-diethylamine-2-hydroxy benzoyl) benzoic acid with 3-methoxy-N,N-di(polyoxyalkylene oxide) aniline. The benzoic acid intermediate is produced in a reversible reaction from N,N-diethyl-m-aminophenol and phthalic anhydride. Since some residual diethyl-m-aminophenol may be present during this subsequent reaction, the intermediate may react with the N,N-diethyl-m-aminophenol to form the xanthene dyestuff. U.S. Pat. No. 6,040,482 improves upon this approach by providing a novel intermediate which does not form a xanthene dyestuff upon reaction with phthalic anhydride. Furthermore, the invention provides an oxyalkylenated xanthene, the physical and chemical properties of which can be easily modified through subsequent reaction of the free hydroxyl groups with electrophiles such as anhydrides, isocyanates, esters, acid chlorides, and the like. However, the reaction of these electrophiles is limited to the availability of the free hydroxyl groups in the oxyalkylenated xanthene, as some of the hydroxyl groups react with the phthalic anhydride to form phthalates during the formation of the xanthene colorant. These phthalates tend to act as impurities with its own unique solubility characteristics. Examples of polyoxyalkylene substituted colorants include those taught within U.S. Pat. No. 5,919,839, and EP 0 896 038 A2 describe phase change, or hot melt inks utilizing the reaction product of an isocyanate (e.g., octadecyl isocyanate) and hydroxyl containing colorant to form a colored urethane wax. These colorants, in order to be utilized within such hot melt ink systems require high purity and complete compatibility within the wax-based ink system. The presence of phthalates, however, in these urethane substituted xanthene colorants reduces the compatibility of these colorants in such wax based ink systems. U.S. Pat. No. 4,833,197 describes an offset ink using diluents, for example, mineral oils with a boiling range of 200xc2x0-350xc2x0 C., and no more than 20% of aromatic components. Again, however, phthalates present within the urethane substituted xanthene colorants remain insoluble in these diluents, thus making these colorants unsuitable for use in these applications.
Thus, even though poly(oxyalkylenated) xanthene colorants have only recently been made available to the colorant market, the utilization of such colorants, particularly made from the intermediate disclosed within the ""482 patent, the use of such colorants has still been limited due to the lack of complete compatibility in wax and/or oil based systems due to the formation of the aforementioned deleteroius phthalates (through the reaction of phthalic anhydride on the free hydroxyls groups of the polyoxyalkylene moieties). There thus exists a need to improve upon this procedure and ultimately to produce a novel intermediate which provides the ability of forming highly desirable derivitized oxyalkylenated xanthene colorants but does not require a multi-step process in forming the intermediate alone which furthermore precludes the formation of deleterious phthalates. To date, the prior art has not accorded such an improvement within this specific area of colorant chemistry. Because of this lack of such a specific type of colorant, the versatility and widespread use of such colorants in different types of inks and substrate has not been accomplished. There is thus a need to provide wax-based ink-jet colorants and compositions which are readily and consistently soluble due to reduction of phthalation products. To date, there have been no improvements for xanthene colorants reducing the possible production of deleterious phthalate impurities thus permitting consistent use within, as one possible end-use, wax-based ink-jet inks.
Therefore, one of the objects of the invention is to provide a urethane-substituted xanthene colorant. Another object of this invention is to provide a synthetic route for a xanthene colorant wherein all reactants are substituted with urethane groups. Another object of the invention is to provide a specific urethane substituted aminophenol intermediate for the production of a urethane substituted xanthene colorant. Still another object of the invention is to provide an intermediate that is an addition product of poly(oxyalkylene)aminophenol and an isocyanate for use in the manufacture of xanthene colorants, particularly rhodamine colorants. A further object of the invention is to provide an addition product of an isocyanate with a specific propoxylated aminophenol intermediate which will alternatively form a xanthene dyestuff upon reaction with phthalic anhydride and thus provides excellent yield of the desired colorant alone. Yet another object of this invention is to provide a relatively inexpensive method for producing such beneficial urethane substituted xanthene (or other type) colorants.
Accordingly, this invention encompasses an aminophenol derivative intermediate comprising at most a total of three moles of a constituent selected from the group of oxyalkylene groups having from 3 to 12 carbon atoms, alkoxy alkylester groups having from 3 to 12 carbon atoms, glycidol, and a glycidyl group wherein said constituent is solely bonded to the armine, and wherein of all of the hydroxyl moieties present on said intermediate, at least one is isocyanate-capped and thus forms a urethane moiety. Since the oxyalkylene groups as noted above, as well as the phenol group (and any others present on the ring, potentially) are reactive, the reaction with a certain amount of isocyanate (such as, without limitation, octadecyl isocyanate) produces the desired urethane moieties thereon. It appears that the hydroxyls on the oxyalkylene, etc., groups react more readily with such isocyanates; thus, a lower molar ratio of isocyanate reacted with the base oxylalkylenated aminophenol should first produce urethanes on the oxyalkylene moieties with the phenol hydroxyl reacting more readily as greater amounts of isocyanate are added. Thus, the compound noted above with at least two urethane groups present on the hydroxyls, as well as at least three urethanes likewise present are preferred as well. Most preferably, at least three urethane groups are present, and such such a preferred specific compound encompassed within this invention is an intermediate conforming to the structure of Formula (I) 
wherein x+y is greater than 0 and less than 4; wherein R is selected from the group consisting of hydrogen, halo, formyl, C1-C20alkoxy, and C1-C20alkyl; wherein Rxe2x80x2 is selected from the group consisting of C1-C10alkoxy, C1-C10polyoxyalkoxy, C1-C10 alkylester, and C1-C10alkyl; wherein Rxe2x80x3 is selected from the group consisting of hydrogen and C1-C4alkyl groups; and wherein Rxe2x80x2xe2x80x3 is selected from the group selected from hydrogen, C1-C24alkyl groups, C1-C24alkoxy groups, and C1-C24ester groups. Preferably R is H, methyl, ethyl, Cl, Br or I, Rxe2x80x3 is hydrogen, methyl, or ethyl, and Rxe2x80x2xe2x80x3 is hydrogen, methyl, or ethyl. In a more preferred embodiment, the N,N-bisurethane-m-aminophenol intermediate is substituted with methyl or ethyl, or is unsubstituted, i.e. R is H. The intermediate is prepared from m-aminophenol or p-aminophenol which is reacted with at most a total of three moles of a constituent selected from the group of oxyalkylenes having from 3 to 12 carbon atoms, alkoxyalkylesters having from 3 to 12 carbon atoms, glycidol, and a glycidyl group wherein said constituent is solely bonded to the amine, and Rxe2x80x2xe2x80x3 is selected from C1-C4alkyl.
Furthermore, the inventive colorant preferably conforms with the structure of Formula (II) 
wherein x+y is greater than 0 and less than 4; wherein R is selected from the group consisting of hydrogen, halo, formyl, C1-C20alkoxy, and C1-C20alkyl; wherein Rxe2x80x2 is selected from the group consisting of C1-C10alkoxy, C1-C10polyoxyalkoxy, C1-C10alkylester, and C1-C10alkyl; wherein Rxe2x80x3 is selected from the group consisting of hydrogen and C1-C4alkyl groups; and wherein Rxe2x80x2xe2x80x3 is selected from the group selected from hydrogen and C1-C24alkyl groups; or any salts thereof (such as salts with inorganic or organic anions, including, without limitation, halides, sulfonates, hydrogen sulfonates, methylsulfates, and the like). Such an aminophenol intermediate in Formula (I) is useful in producing the xanthene colorant of Formula (II).